Scuba type air supply tanks are pressurizable aluminum or steel cylinders having a single port through which the cylinder is charged and through which air is later supplied to the diver for use in breathing. The port is internally threaded and a manual control valve is mounted therein. The usual control valve includes an elongated tube which extends a few inches into the tank to prevent sediment or liquid from exiting the tank.
In order to prevent foreign matter from entering the tank during the charging operation it is common practice to connect a filter between the outlet of the compressor and the control valve. Unfortunately, this filter is not always used, and as a result, impurities do on occasion enter the tanks. Also, corrosion within the tank itself can result in sediment being formed in the tank and being entrained in the air supplied therefrom to the diver.